Method of and machine tool for rolling the toothing of gears into a crowned shape

ABSTRACT

The invention is directed to the method and apparatus for forming a gear by rolling wherein the blank in engagement with roller gears is rotated about its axis. Simultaneously a small relative oscillating or tumbling movement is executed between the gear blank and the roller gears with the rotational speed of the gear blank being different from the single oscillation frequency or its integral multiple. The various oscillation movements to provide the gear toothing with radial and/or axial crowns of different values. It is also possible to separately impart predetermined amounts of radial and axial crowns to the formed gears.

United States Patent Inventor Frank F. Erdelyi 313 Foxhall St., Raleigh, NC. 27609 Appl. No. 794.713 Filed Jan. 28,1969 Patented June 15, 1971 METHOD OF AND MACHINE TOOL FOR ROLLING THE TOOTHING OF GEARS INTO A CROWNED SHAPE 27 Claims, 20 Drawing Figs.

[56] References Cited UNITED STATES PATENTS 3,394,570 7/1968 Erdelyi 72/107 3,455,139 7/1969 Flowers et a1 72/365 Primary E.taminerLowell A Larson Attorney-Beaman & Beaman ABSTRACT: The invention is directed to the method and apparatus for forming a gear by rolling wherein the blank in engagement with roller gears is rotated about its axis. Simultaneously a small relative oscillating or tumbling movement is executed between the gear blank and the roller gears with the rotational speed of the gear blank being different from the single oscillation frequency or its integral multiple, The various oscillation movements to provide the gear toothing with radial and/or axial crowns of different values. It is also possible to separately impart predetermined amounts of radial and axial crowns to the formed gears.

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METHOD OF AND MACHINE TOOL FOR ROLLING THE TOOTI'IING OF GEARS INTO A CROWNED SHAPE BACKGROUND OF THE INVENTION The invention relates to a method of and tool for rolling a crowned tooth on gears.

In the gearing construction industry crowned gears are used, predominantly with a view to reducing the noise and pressure between the tooth flanks. Said crowned gears are, in addition, more insensitive to any fitting inaccuracies than uncrowned gears. In the case ofcrowned gears, a difference must be made between a longitudinal crown and a radial crown. Both types ofcrowns, as a rule, are even used interchangeable.

It is known to obtain the crown of the tooth immediately when making the tooth proper. This is effected in particular when grinding, milling and trimming (especially planing) the teeth. But it is also known to obtain the crown in a cutting process when the tooth proper has been finished. In this operation, the crown is obtained, for instance, by scraping.

The invention is concerned with the problem of developing a method and a machine tool for rolling the teeth of gears with crowns wherein the crowned teeth may be produced both by hot and cold rolling.

The following statements relate especially to the formation ofa crowned tooth by cold rolling.

In the rolling operation, the workpiece rotates on the one hand about its own axis, the rolling axis. In addition, the rolling tools which engage the circumference of the workpiece are capable of rotating about their own axis. Either the rolling tools or the workpiece, or even both, must be driven.

In this operation, the position of the rolling tools with respect to the workpiece may be unchanged in an axial direction. In this case, the feed of the rolling tools into the workpiece takes place radially.

But it is also possible-and this is in general preferred when practicing the invention-that the workpiece in addition to its rotary movement about the rolling axis also performs an axial movement in the direction of the rolling axis with respect to the stationary rolling tools, i.e., roll gears, which are, however, capable of rotary movement. In this case, the teeth are applied to the surface of the tool in the form of a helical line, which surface, in the case ofa spur gear is a cylindrical surface and, in the case of a bevel gear, is formed by a conical surface.

SUMMARY OF THE INVENTION The invention may be practiced in that the crowned teeth are formed completely in a rolling process from a cylindrically or conically shaped blank. Preferably, however, the invention is carried out in such a manner that the teeth ofthe workpiece are produced beforehand in some other way, especially by milling, planing, trimming, or grinding, and the gear is provided with the crowning only thereafter, by the rolling process in accordance with the invention. By this additional rolling of the teeth which imparts thereto the desired crown in the longitudinal and/or the radial direction, the surfaces of the tooth flanks are simultaneously compacted. One may in addition carry out in this connection a correction of the tooth profile.

Accordingly, contemplations will be based in the following on a workpiece having already been provided with teeth without restricting, however, the invention to such an embodiment.

In accordance with the invention, the workpiece, on the one hand, performs with respect to the rolling tool a rotary movement about its own axis, the rolling axis, and, on the other hand, a tumbling or oscillating movement with respect to the rolling axis along the shell ofa double cone, the apex ofwhich lies in the rolling axis, the speed of the workpiece about its own axis and the frequency of the additional tumbling movement differing from each other.

The term differing means a difference such that no synchronous movement will result. The rotary speed thus must not be equal to the tumble frequency nor equal to a frequency obtained by multiplication or division of said frequency by an integer.

The process may be carried out simply by modification of known gear-rolling machines. It will lead to a gear with both a longitudinal or axial and a lateral or radial crown, as well as finally to a combined longitudinal and lateral crown in an extremely simple manner.

Preferably, the process is carried out in such a manner that the apex of the cone shell with the tumbling movement of the rolling tool thereon is arranged approximately in the center of the workpiece when looking in the axial direction thereof. With this process, the longitudinal crown is distributed in the axial direction of the workpiece in a uniform manner so that the bearing pattern will form in the center of the gear when looking in the axial direction.

If only a radial crown is to be produced, then, in accordance with the invention, the base of said cone of the tumbling movement becomes a straight line, along which the workpiece is oscillating with respect to the rolling tool and which line is disposed in the plane determined by the axis of the rolling tool and the rolling axis.

If, however, only an axial crown, longitudinal of the tooth is to be produced, the base of the cone shrinks as well to a straight line along which the workpiece oscillates with respect to the rolling tool and which line is disposed vertically with respect to the plane determined by the axis of the rolling tool and the rolling axis.

If both a radial and an axial crown is to be produced, the base of a cone of the tumbling movement will form an area with a steady definition, especially a circular or elliptic area.

The absolute amplitude of the tumbling movement, of course, will be the greater, the wider is the distance from the cone apex which lies in the rolling axis. The amplitude of the tumbling movement is governed by the respectively desired value of the axis and/or radial crown.

In a machine tool to carry out the method of the invention, the gear blank may be clamped between the punch tapers which are disposed eccentrically with respect to the rolling axis on the surfaces of a double cone, the points of which are disposed in the rolling plane.

Another embodiment of the process in accordance with the invention is characterized in that the workpiece is supported on a self-aligning pivot or ball bearing arranged in the rolling axis by its one side and is supported on a projection which may have a tumbling movement from the other side of the workpiece imparted thereto.

In this arrangement, the workpiece is preferably arranged on a centering projection which, together with the receiving journal, is provided eccentrically on the centrically arranged pusher in such a manner that the centering projection with the receiving journal performs a tumbling movement along the conical shell, the cone apex of which lies in the rolling axis, and that the workpiece takes support on an abutment or intermediate member which is rotatably supported on the receiving journal with the aid ofa radial and an axial bearing. As a rule, it will be recommendable to practice the invention in such a manner that the tooth has imparted thereto both an axial and a radial crown. In case only one crown is to be produced, the cone of the tumbling movement will accordingly have shrunk to a triangular area along which the workpiece moves back and forth with respect to the rolling tools. Also in the case of this arrangement, it will be recommendable to take as a basis a conical movement of the workpiece. The tool has then imparted thereto an additional movement with respect to the rolling tools by which the conical movement in the one or other direction is suppressed according to the desired type of crown. For an explanation of the invention it has up to now been assumed that the workpiece proper performs the tumbling movement. What is important, however, only is that the described relative tumbling movement is performed between the rolling tools and the workpiece. It is accordingly also possible to have the rolling tools carry out the tumbling movement. Furthermore a rolling head may perform said tumbling movement in which head the rolling tools are supported rotatably. Here as well it is important that the tumbling movement is performed along a cone wherein the frequency of the tumbling movement must differ from the speed of the workpiece during the rolling operation.

Another embodiment of the invention makes it possible to roll crowned bevel gears by means of an auxiliary device which may be used in a plurality of known machine tools. Also with this embodiment either the workpiece or the rolling gear is arranged in such a manner that it performs a swinging or tumbling movement about the axis of the rolling head or of the machine, wherein, however, the apex of the tumbling cone is not disposed in the center of the workpiece.

It has been found in the production of high-speed gearings that it is necessary to separate the axial crown of a tooth from the radial crown and to determine the values thereof independently from each other. With the known devices and tools, such as grinding devices and scraping wheels, used for shaping crowned gears, it is not possible to perform the profile correction necessary to effect a separation. A separate profile correction of a tooth is so expensive that it cannot be carried out for economical reasons.

The last embodiment of the invention allows for the provision of a crown with a radial as well as an axial component thereof being adapted to be determined independently from each other.

The profile of the rolling tool tooth, for instance a rolling rod or a rolling gear, is formed by taking as a basis the theoretically calculated tooth of the workpiece, as a counterprofile or counter evolvent in such a manner that it is deformed from the basic shape of the rolling tool tooth according to the desired crown of the tool. It is possible by such counterprofiles to form the axial and radial crowns independently from each other.

If the rolling tool, for instance, is corrected exclusively for radial crown then an axial crowns may be obtained by a simple linear tumbling movement of the workpiece axis. It is also possible to obtain a maximum value for the axial crown by a corresponding profilation of the rolling tooth and a movement of the workpiece axis, while the radial crown may assume any value between zero and a maximum value. On the other hand, under certain circumstances, the tumbling movement may be fully dispensed with in case the desired radial and axial crowns may be obtained solely by corresponding correction of the tooth profile of the rolling tool teeth.

BRIEF DESCRIPTION OF THE DRAWING The invention will now be explained in more detail by way of the enclosed drawings. In the drawings,

FIG. 1 shows a lateral view ofa known gear-rolling machine which may be used to practice the invention,

FIG. 2 shows a longitudinal sectional view of parts of the transmission of the machine of FIG. 1 to represent a pusher, an ejector and the rolling wheels together with the master wheel,

FIG. 2a shows an enlarged longitudinal sectional view ofthe arrangement of the master wheel and the movable contact piece of FIG. 2,

FIG. 2b shows an enlarged longitudinal sectional view ofthe arrangement of the pusher and the freely movable contact piece of FIG. 2,

FIG. 3 shows a longitudinal sectional view of parts of the transmission of a gear-rolling machine modified within the frame of the invention, wherein the rolling wheels are driven by a central transmission, Unit B, via movable shafts, for instance, arcuate tooth couplings,

FIG. 3a shows an enlarged representation of the arrangement of the workpiece guide in accordance with FIG. 3 by means of eccentrically supported center points,

FIG. 4 shows a plan view, partially in section, taken on another embodiment of the gear-rolling machine, wherein the workpiece only performs a rotational movement about its own axis and the necessary tumbling movement is performed by pivotally moving the pivotally supported rolling head, gear unit C,

FIG. 5 shows a plan view of the left-hand side of FIG. 4 with a hydraulic unit and limiting screws to limit the tumbling movement of the rolling head,

FIG. 6 shows a plan view taken on the right-hand side of FIG. 4 representing a device with a measuring instrument to control the tumbling movement,

FIG. 7 shows a top plan view taken on the device shown in FIG. 4 with a pair of zero switches to neutralize the tumbling movement during the main rolling process,

FIG. 8 shows a side view of a spur gear and on the rolling wheel cooperating therewith to diagrammatically illustrate an embodiment of the invention,

FIG. 9 shows a plan view ofa spur gear and the rolling wheel diagrammatically illustrating another embodiment of the invention,

FIG. 10 shows another diagrammatic side view of a workpiece and rolling wheel cooperating therewith to illustrate another embodiment of the invention, looking in the direction of the arrow X of FIG. 11 with the elimination of the rolling wheels 2a and 2b of said FIG.,

FIG. II a view taken on FIG. 10 in the direction of the arrow XI,

FIG. 12 shows a view taken on a device for the production ofa bevel gear provided with a crowned formation,

FIG. 13 shows a view taken in the direction of the arrow XIII on the representation of FIG. 12,

FIG. 14 shows a longitudinal sectional view taken on an embodiment of the invention which may be used on bevel gear rolling machines or other machine tools as an auxiliary device to roll the teeth of bevel gears of all types with a crowned formation, wherein at least one pinion serves as a rolling wheel,

FIG. 15 shows a longitudinal sectional view according to FIG. 14 with the rolls of workpiece and rolling wheel being exchanged as compared with FIG. 14,

FIG. 16 shows an enlarged representation of a theoretically calculated rolling profile of a rolling tool according to another embodiment of the invention, wherein the profile is corrected according to the desired radial crowned formation, and

FIG. 17 shows a plan view taken on the rolling tooth profile shown in FIG. 16, which is corrected in accordance with the desired axial crowned formation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As already explained above, many types of gear-rolling processes and gear-rolling machines may be employed to carry out the invention. The invention will now be described by way of the gear-rolling process and the gear-rolling machine which has been described inter alia in the Austrian Pat. letter 260,663. This Austrian patent letter relates to a process and apparatus for producing, compacting and/or correcting the profile of toothings on cylindrical members of all types capable of rotation by rolling, and is characterized in that the teeth take as a basis, base profiles having no edges and is applied in the form of a helical line on the surface of the cylindrical workpiece by at least three simultaneously engaging rolling wheels, the teeth of which is designed as the counter evolvent to the desired teeth calculated of tooth gaps. First to follow now is a prescription of the machine used to practice the invention, by way of the FIGS. 1 and 2. May it be emphasized that the invention is restricted neither to the process described here nor the examples of embodiments shown in the drawings. The process may be employed after the necessary modification of the known gear-rolling machine and devices.

To practice the invention, use may be made of a machine with a machine body A, having supported therein a shaft 9 from which the drive of the individual machine parts is effected. The shaft is driven by an electric motor, not shown, supported in the lower portion of the machine body A with a driving pulley and a driven pulley l0 fastened on the shaft 9.

Housing units B, C, D and E are fastened on the machine body A. The housing unit B serves to support a master wheel 8, please see FIG. 2, which simultaneously serves as a drive for the rolling wheels 2, 2a, 2b and as an ejector. The housing unit C serves to support the rolling wheels 2, 2a and 2b, while the housing unit E serves to support the pusher 11. The housing unit D accommodates a supply container 12 and the parts for the supply of the workpiece and the discharge of the finished gear.

A workpiece l is brought into the charging position by hand or preferably from a supply container 12, and brought into the operating position by means of the pusher 11.

Prior to starting the rolling operation, the workpiece I will engage on the end face 13 of the master wheel 8, please see FIG. 2a, where it is laterally centered and clamped tight. After the workpiece has been clamped tight, the pusher 11 and the master wheel 8 will have imparted thereto a rotary movement 14 and simultaneously an axial feeding movement, thus starting the rolling operation.

The pitch of the toothing of the master wheel 8 thus must correspond as exactly as possible to the desired pitch of the gear to be rolled. The further design of the teeth of the master wheel, by the way, is not important and may be the same as the teeth of the workpiece. I

For the purpose of centering the workpiece, the pusher 11 may also be provided with a centering projection 15, which cooperates with a corresponding centering bore 16 of the workpiece, (please see FIG. 2a, 2b). Also the end face 13 of the master wheel 8 could be provided with a corresponding centering bore or a centering projection for the same purpose, cooperating with a corresponding centering device of the blank.

In the housing portion C, three rolling wheels 2, 2a, 2b are provided in the example of embodiment which are uniformly spaced over the circumference and arranged about the common axis of the workpiece l and the master wheel 8. For the purpose of an exact centering and toothing of the workpiece, the arrangement of three rolling wheels 2, 2a and 2b is preferred.

Eccentric shafts 17 serve to support the rolling wheels 2, 2a and 2b, on which the rolling wheels are loosely supported for rotation with the aid of needle bearings 18. The eccentric shafts 17 are eccentric with respect to bearing journals 19 which are loosely supported for rotation in the housing part C.

The rolling wheels 2, 2a and 2b are in mesh with the teeth of the master wheel 8 and are driven by the master wheel in the example the embodiment of FIG. 2. Instead of this, the rolling wheelsas is shown in FIG. 3-may be driven directly. It is also possible to drive the workpiece proper instead of making use of any of the above two possibilities shown in the drawings.

The master wheel 8 is fastened on a tailstock 20 which is rotatably supported in the housing portion B. In a corresponding manner, the pusher 11 is fastened at a tailstock 21 which is rotatably supported in the housing portion E. In the example of the embodiment in accordance with FIG. 2, both the master wheel tailstock 20 and the tailstock 21 are driven for rotation by the driving shaft 9 in a manner to be described in more detail hereinafter.

To adjust the forming pressure, a hydraulically or otherwise actuated gear and ring gear 22 are provided, which is loosely supported for rotation about the axis of the master wheel 8 on the housing portion C. For this purpose a concentric bushing 23 is provided at the housing portion C on which the wheel 22 is rotatably supported by means ofa needle bearing 24.

This wheel 22 is provided with three replaceable tooth segments 25 which together form an internal teeth in mesh with the tooth segments 26 fastened on the bearing journal 19 of the eccentric shafts 17. The tooth segments 25 and the tooth segments 26 thus form a gearing.

In addition to the tooth segments 25 formed as internal teeth there are external gearing provided on the outer periphery of the wheel 22, which are in mesh with a rack 28. The rack 28 is designed as a threaded sleeve, the threaded inner bore of which is screwed onto the thread of a threaded spindle 29.

The rack 28 serves to adjust the wheel diameter and the tooth depth. The rack 28 is connected with the external teeth of the wheel 22 in such a manner that an axial movement of the threaded spindle 29 causes a rotary movement of the eccentric shafts 17-17. The position of the rack 28 and thus the position of the eccentrics l7 and the radial position of the rolling wheels 2, 2a and 2b, respectively, is adjusted by rotation of the threaded spindle 29 by means ofa handwheel 31.

As already explained above, the drive of the rolling wheels 2, 2a and 2b, may be carried out in any suitable manner. In the embodiment of the invention shown as an example in FIG. I and FIG. 2, a center drive has been selected, in which the master wheel 8 simultaneously serves as a drive wheel for the rolling wheels 2, 2a and 2b. The master wheel 8, which determines the exactness of the pitch accuracy of the workpiece, is fastened in a conical recess 33 of the ejector tailstock 20, which is supported nonrotatably, but axially displaceably, in a driving gear 34. The driving gear 34 is in turn rotatably supported in the housing B and is in mesh with an intermediate gear 35 which again is in mesh with a gear 36 driven by the drive shaft 9.

An axial movement 37 and an axial movement 38 opposed thereto are provided for the ejector or master wheel tailstock. A hydraulic unit 39 is arranged in connection with these movements, please see FIG. 1, with is rotatably but axially nondisplaceably connected with the ejector tailstock 20 by means of a coupling 40. Opposite the ejector tailstock 20, but on the same axis therewith, there is arranged the tailstock 21 ofthe pusher 11; it is freely rotatably supported in the housing E. In the example of the embodiment, please see FIG. 2, the tailstock 2] it is positively driven the same as the tailstock 20. The ratios of the drives of the tailstocks are different so that the pusher tailstock has a lower speed than the ejector tailstock.

The forming pressure of the. rolling wheels is determined by adjusting the hydraulic pressure of the pressure fluid for biasing a hydraulic unit which tries to rotate the wheel 22 in a corresponding direction.

After termination of the main forming process, the tooth profiles of the workpiece are further refined by momentarily shifting the direction of rotation ofthe rolling wheels 2, 2a and 2b. Following the main forming process the rolling head-unit C in FIGS. 4 to 7is again laterally pivoted from its concentric axial position. The pivotal movement of the rolling head may be determined in the manner shown in FIG. 5 with the aid of adjusting screws 84, 84a and a hydraulic unit 83, and controlled by a measuring instrument 8.5 which simultaneously serves as a controlling device for the amount of crown of the workpiece toothing. The counter evolvent teeth of the rolling wheels 2, 2a and 21:, however, remains in engagement with the rolled teeth which is subsequently rolled with an amount of crown in that now therolling head, unit C in FIG. 4 returns to its center position or exact axial position, respectively, and only the surface of the teeth are refined and compacted, respectively, and the profile corrected.

The two working spaces of the hydraulic unit 44, please see FIG. 2, may remain unbiased all the time in that now only the hydraulic working medium from the side that had been biased by then, under certain circumstances, flows over a throttle. This will be necessary even if the workpiece 1 has been positively clamped between the pusher lll and the end face 13 of the master wheel 8. The hydraulic fluid draining via the throttle now in turn supplies the abutment force which, of course, during these profile refining and surface compacting operations is by far smaller than during the actual rolling process.

Thereafter, the gear 22 is shifted to the opposite direction by the above mentioned hydraulic unit, whereby the rolling wheels 2, 2a and 2b are moved out of the workpiece l to such an extent that the workpiece 1 is relaxed. The hydraulic unit 39 of this ejector tailstock 20 has been shifted to the opposite direction already before. Now, also the hydraulic unit 44 of the pusher tailstock 21 is shifted to the opposite direction in that now the piston of the said unit is biased with hydraulic fluid from the left in FIG. I. In this manner the ejection of the finish-rolled gear is performed. In this ejector movement, the pusher tailstock 21 may be withdrawn more quickly than the ejector tailstock because now the workpiece I does no longer have to be positively retained.

The rolling rolls 2, 2a and 2b are provided with an inlet and outlet cone in a manner known per se. The profile thereof is shown in detail in the Austrian Pat. letter 260,663 and does not have to be described here in any more detail. For practicing the invention, by the embodiments of FIGS. 4-7, the machine just described may be used with only slight modification.

In the diagrammatic representation of FIG. 8, the workpiece is designated with 1 and one of the rolling wheels is designated by 2. The workpiece 1 rotates about the axis 30, while the rolling wheels 2, 2a and 2b are stationarily supported and may rotate about their own axis 46. The workpiece may in addition perform an axial movement in the direction of the arrow 37, 38, please see FIG. 1. Either the workpiece 1 or the rolling wheels 2, 2a and 2b or both, are driven in a manner not shown in more detail. In addition to the movements described the workpiece performs a tumbling or oscillating movement 4 about the point 7 which lies in the rolling axis 3. It tumbles back and forth in this operation along a straight line 4a, lying in the plane in which also lie the rolling axis 3 and the axis 46. The size of the distance 4 about the workpiece tumbles back and forth, of course, is dependent on the distance of the measuring spot from the apex 7 of the cone and is governed by the desired amount of crown. With the justdescribed tumbling movement along a straight line 40, there results a radial or lateral amount of crown. The tumbling movement of the axis of the workpiece 30 takes place along a cone 4 which is here flattened into a triangle lying in the plane ofthe rolling axis.

FIG. 9 shows the process of producing exclusively a longitudinal or axial amount of crown. In this case, the apex of the cone is again referenced 7. The distance or the triangle 5, respectively, by which the axis 3a of the workpiece I tumbles back and forth, now, however, is arranged vertically with respect to that plane in which the axis 36 of the rolling tool and the axis 3a of the workpiece lie.

A preferred embodiment of the invention is shown by way of FIGS. 10 and 11, wherein both a longitudinal or axial amount of crown and a radial or lateral amount of crown are generated. In this case, the workpiece l likewise has imparted thereto a tumbling movement about the peak 7 which lies in the rolling plane 3b.

All the points of the axis 3a of the workpiece 1, which perform this tumbling movement, however, now lie on a cone 6, the base of which is formed by a circular area 47. Independently of this, both the workpiece and the rolling wheels perform a rotary movement, and the workpiece an axial move ment 42. As will be seen from FIG. ll, preferably three rolling wheels 2, 2a and 2b are provided to carry out the rolling operation.

FIGS. 12 and 13 show schematically the embodiment of the invention to produce an amount of crown on a bevel gear. The rolling wheels, or tool wheels, here as well are designated with 2, 2a and 2b and are driven in the sense of the arrows 48,4811 and 48b shown in the drawing. The workpiece which preferably has already prefabricated teeth, bears the reference numeral la. It performs a tumbling movement 6 about the cone apex 7 in addition to its rotary movement 49 about the rolling axis 3, said cone apex 7 being disposed in the rolling axis 3. Also in this case the axis of the workpiece Ia moves in the plane 6 ofa cone having a circular base 47. The workpiece 1a is spherically or universally movably supported on its side facing away from its accommodation spindle lb. The tumbling drive corresponding to the tumbling cone and the spherical support may be constructionally designed in a manner similar to the embodiment shown by way of FIGS. 2a and 2b. The

workpiece la, in this operation is kept concentric by rolling wheels 2, 2a and 2b, and the rolling pressure exerted in the axial direction is used as feed of the workpiece.

As already explained, the apex 7 of the cone does not necessarily have to be disposed in the center of the gear when looking in the axial direction thereof. The base of the cone may have any suitable outer contour. As a rule, however, a circularly or elliptically shaped base will be recommendable.

The manner in which the tumbling movement of the workpiece with respect to the rolling tools provided in accordance with the invention, may be constructionally obtained is represented in some more detail by way of FIGS. 3, 3a. Here as well the workpiece is designated with l and is fastened on the journal 51, 51a. The rolling tools are referenced 2, 2a and 2b as before and are driven by gear transmissions 52 of the unit B in the sense of the arrows 48 whereby the workpiece 1 has imparted thereto a rotation in the sense of the arrow 54. There are provided in this arrangement altogether three tools 2, 2a and 2b which are uniformly spaced about the periphery of the workpiece l and are in mesh with the workpiece teeth.

The gears 58, 5811 as well as the gears 58b and 580 and the holders 60 and 60a of the peaks of the bodies 53 and 530 are driven via the driving shaft 55 and the gears 56, 56a, and 56 and 560 at a speed different from the speed imparted to the workpiece 1 by the rolling wheels 2, 2a and 2b in the sense of the above explanations. Each of the holders and shafts 60, 60a, respectively, has a center point 53 and 53a, respectively. The center point 53a, however, is offset by with respect to the center point 53. Both shafts are driven in the sense of the arrows 62 and 62a, i.e. in the same sense, by the shaft 57 and 59, respectively, at a speed unlike that of the rotation of the workpiece l. The eccentricities 63 and 63a of the two center points are selected in correspondence with the length of the individual axle journals. When driving the center points 53 and 530 from the shaft 57 or 59, respectively, thus, the workpiece has imparted thereto a tumbling movement 47 wherein the centerline 3a of the workpiece 1 moves about the rolling axis 3 on a cone surface 47, FIG. 10, with the two cones 6 and 6a, the peaks 7 ofwhich are lying in the plane 3b, and intersects the rolling axis 3 in this plane.

The type of the drive of the three rolling wheels 2, 2a and 2b of this embodiment of the invention is shown in FIG. 3. The three rolling wheels may also mesh with a master wheel in the manner as shown in FIG. 2 which master wheel corresponds exactly to the pitch of the teeth of the workpiece 1. The drive of the rolling wheels 2, 2a and 2b may also be effected directly from this master wheel 8. All this may be designed in correspondence with the machine of FIGS. 1, 2, 3 and FIGS. 4 to 7, respectively.

The device of FIG. 2 is based on that of FIG. 1. The ejector 20 and the master wheel 8 thus are again rotatable and are arranged to be axially displaceable in both directions. The same applies equally also with respect to the pusher 11. With FIG. 2, however, to carry out the invention, the ejector 20 and the master wheel 8 are driven at a speed different than that of the pusher 11. For this purpose, a different gear ratio is arranged between the ejector 20 with pusher 11. The ejector 20 and the master wheel 8 are driven via the gear train of the unit B at a speed which, for a certain embodiment, is n=350 minl, for example.

A contact member 64 is provided in the rolling axis 3 on the master wheel 8, said contact member projecting beyond the right-hand end face of the master wheel 8 in FIG. 2. The contact member 64 is supported by a pivot bearing 65 having a spherical surface 66 the center 67 of which is disposed in the rolling plane 3b. The pivot bearing 65 in turn is supported in a screw nut 68 which is screwed onto the tailstock 20 and simultaneously serves to hold the master wheel 8. Towards the outside, the contact member 64 is held while maintaining a sufficient play by means of a threaded ring 69 screwed into the master wheel 8 so that the contact member 64 may spherically move along the surface 66 about the point 67 which is disposed in the rolling plane 3b.

The conical surface 70 of the tailstock 21 ofthe pusher 11 is disposed centrally with respect to the rolling axis 3 with which that transmission unit E coincides. On the tailstock 21, however, a reception journal 71 is provided, the axis of which is disposed eccentrically obliquely with respect to the rolling axis 3 and the axis of the transmission unit E. The eccentric axis 72 intersects the rolling axis 3 in point 73. As will be seen from the representation, in the example of the embodiment, FIGS. 2, 2a, 2b, the eccentricity of the reception journal 71 is provided in such a manner that this eccentricity is 0.8 mm. at a distance of 195 mm. from point 73. The degree of the eccentricity is governed by the degree of crowned formation desired to be generated on the teeth ofthe workpiece 1.

The reception journal 71 is provided with a centering projection on its outwardly pointing left end onto which the workpiece may be pushed. The centering projection 15 is disposed concentrically with respect to the eccentric axis of the reception journal 71. A contact member 75 is loosely supported for rotation on the eccentric reception journal 71 with the aid of a radial antifriction bearing 76and an axial antifriction bearing 77. The axes of these bearings and this contact member 75 are concentric with respect to the eccentric axis 72.

The workpiece 1 is pushed onto the centering projection 15 whereupon the pusher 11 presses the workpiece 1 against the projecting extension of the contact mentber 64. The machine may now be set to work with the workpiece 1 being rotated simultaneously from the master wheel 8, which at the same time synchronizes the drive of the rolling wheels 2, 2a and 2b, namely, in the example of the embodiment at a speed n=350 min l. In this operation, the workpiece I rotates on the eccentric centering projection 15. The center 73 of the cone surface 74 coincides with the rolling axis 3 of the workpiece in that the eccentric axis intersects the rolling axis.

The speed of the centering journal 15 and the eccentric reception journal 71 in the example of embodiment of FIG. 2 is about half the speed at which the workpiece 1 is driven about the rolling axis 3 by means of the master wheel 8 and the rolling wheels 2, 2a and 2h. The workpiece 1 at this low speed has imparted thereto an additional tumbling movement about the point 67 which during the rolling operation coincides with the point 73. The eccentric axis 72 in this operation moves on a cone surface 47, FIGS. 10 and 11, whereby the teeth of the workpiece has imparted thereto both a radial and axial amount of crown.

With this rolling operation the contact member 75 lies closely against the workpiece 1 and thereby rotates at the higher speed of 350 minl on the reception journal 71, which has the lower speed of for example n=1 7 l .875 minl The axial force which is necessary for the workpiece'l to be taken along by the master wheel 8, in this arrangement, is exerted on the contact member 75 by the hydraulic unit 44 of the pusher 11 via the axial antifriction bearing 77.

An introducing transmission 79a, 79b, 79c, 79d, and 79, please see also FIG. 2, is driven by the main shaft 9, and is fastened in the machine stand A. The gear 79c is formed of two members 79b and 81 corresponding to each other; rotatably supported on bearing journals 80 and provided to be radially adjustable by means ofa screw connection 82. This introduction gearing or introduction gear 79d, respectively, serves the purpose of synchronizing from tooth to tooth the teeth of the workpiece 1 to be provided with a crowned toothing, exactly into the tooth gaps of the rolling gears 2, 2a and 2b or the master wheel 8, respectively. The drive of the in troduction wheel 79d takes place positively via the just described transmission from the drive shaft 9. The exact position of the introduction wheel 79d may be adjusted with the aid of the screw connection 82 of the intermediate gear 79b and the subdivision 81 thereof.

FIG. 14 shows an embodiment of the invention by means of which the teeth of a bevel gear may have imparted thereto both a longitudinal or axial amount of crown and a radial or lateral amount of crown.

For exact guidance, the workpiece wheel 86 is pushed onto a rotary member 87 which is loosely supported for rotation on ajournal 103 with the aid ofa radial friction bearing 83 and an axial ball bearing 89. The journal is connected with the main shaft 90 ofa known bevel gear rolling machine, not shown, (or a bevel gear coining machine, a lapping machine or other machine tools, such as milling machines or latches). To roll the crowned formation, a rolling wheel 91, the axis of rotation of which forms an angle of 90 with the axis ofthe shaft 90, engages, with the workpiece wheel 86. To increase the output of the device, several rolling wheels 91!: may be provided of which, however, only one needs to be driven.

If bevel gears are rolled with a crowned formation by means of a tumbling movement, differences in pitch may occur on the pitch circle, and the rolling wheels synchronized with respect to each other will have to be arranged with a tooth clearance adapted to the tumbling movement.

The axis 93 of the workpiece-receiving arrangement 87 and thus of the workpiece 86 are disposed eccentrically obliquely of the axis 92 of the rolling head and/or the rolling machine. The rolling plane is represented by the track line 9494. The point of intersection 95 of the axis 92 and 93 is to be defined as follows:

The teeth of the bevel gear 86 are tapering in the direction towards a cone apex. An angle of 90 is applied to the junction line from the cone apex to the center 96 of the workpiece toothing 97 in the point 96. The point of intersection of the free leg of this angle with the axis 92 is the point of intersection 95 which has to be found, that means the pivot point of the tumbling or pivotal movement which is necessary to roll a crowned formation. The point 95 thus is the center of the contact circle of a tangent represented by the junction line of the points 86 and the mentioned cone apex in the contact point 96. The point of intersection 95 no longer lies in the rolling plane as is the case with the example shown in FIG. 2b. The center point 98 of the rolling plane 94-94 is pivoted outwardly in correspondence with the value of the desired crowned formation 99 of the bevel gear toothing '97, from its position on the rolling head plane 92, so that the workpiece axis 93 rotates on a cone surface about theaxis 92 thus describing a circular path 100 on a plane vertical with respect to the axis 92 with the point 95 disposed on the cone apex as the center of the movement. Thus, in addition to the main cone 101 described by its intersection triangle 96--9596, the secondary cone 102 will still have to be taken into consideration which is described by 95 and the circular path 100; both cones 101 and 102 have the point 95 for a common apex. Also the center of the ball belonging to the annular spherical surface element 104 containing the points 96 coincides with this point, said spherical surface element being determined by the tumbling movement of the axis 93 and causing; the desired amount of crowned formation of the bevel gear teeth. The crowned for mation of the teeth may be adjusted by the adjustment or limitation, respectively, of the degree of the pivotal movement of the tumbling movement. For a more uniform profiling of all the teeth of the workpiece wheel 96 the speeds of the workpiece wheel and the rolling machine must differ from each other.

The generation of the crowned formation 99 of a bevel gear 86 also in this example of embodiment is obtained by a tumbling movement which-as will be seen from FIG. 14-is caused by obliquely supporting the workpiece reception arrangement.

In accordance with FIG. 15, the device first shown in FIG. 14 may be used also for rolling with a crowned formation the teeth 105 ofa pinion 107 belonging to the bevel gear 86. With this embodiment of the invention, a rolling wheel 106 is pushed onto the rotary member 87 instead of the workpiece wheel 86, the workpiece, i.e. the pinion 107 engaging in said rolling wheel 106. In this embodiment of the invention, thus, the rolls of the rolling wheel and of the workpiece wheel have been inverted as compared with the embodiment shown in FIG. 1. Therefore, the center of the section of the spherical area 109 no longer coincides with the point of intersection 95 but falls on the extension of the distance to be determined by 95 and the center point of the rolling wheel teeth, beyond the tooth center and, secondly, on the circle with the length ofthe distance about said center. Also with this embodiment, the tumbling movement determines a section of the spherical surface which causes the desired crowned formation of the pinion teeth. To increase the output several pinions may be rolled with a crowned formation simultaneously with one and the same rolling wheel.

Another embodiment of the device for rolling the teeth of gears with a crowned formation is described by way of FIGS. 16 and 17 by means of which the teeth may again have imparted thereto both an axial or radial crowned formation. But the embodiment allows for the amount of axial crown to be separated from the amount of radial crown and for both to be determined independently of each other.

FIG. 16 shows the tooth profile ofa rolling tool 110, for instance, ofa rolling wheel or a rolling rod, which has been corrected as a counter profile corresponding to the radial or lateral crowned formation of the workpiece teeth. The FlG. shows in outline the basic shape of an evolvent tooth by the dotted line 111-111. The profile correction of the rolling tool teeth needed for rolling with a crowned formation, restriction of certain tooth gap regions, is described by the solid line 112-112. No profile correction is carried out on the pitch circle and in the tooth center 113. From the center of the tooth to the foot 114 of the tooth, the tooth gap is steadily reduced by an amount up to 114a and 1141;, respectively, at the foot. ln the same manner, the tooth gap of the original evolvent toothing 111-111 is reduced by the amount 115a and 115b, respectively, at the tooth peaks 115. These restrictions of the tooth gaps of the rolling tool will cause the corresponding crowned formation of the workpiece teeth in the rolling process, the teeth of the workpiece having imparted thereto a radial crowned formation corresponding to the curvatures of the rolling teeth. An axial crowned formation may be obtained by means of the tumbling movement which has already been described.

FIG. 17 shows the design ofthe rolling tooth of a rack or of a rolling wheel which has been corrected as counter profile corresponding to the axial or longitudinal crowned formation of the workpiece teeth. In the figure the basic shape of the rolling tool teeth is shown in outline by the dotted lines 116a, 116b, 1160 and 116d. At the tooth peaks, the solid lines 1170 and 117b describe the corrected profile; on the base of the tooth gap the solid lines 118a and 1181;. To avoid a tooth play and the displacements of the profile connected therewith the original teeth of the rolling tool is not corrected along the pitch circle 119 and in the tooth center.

With this embodiment of the invention it is possible for the first time to produce gears with teeth having either an axial or a radial crowned formation or with a desired ratio of axial and radial crowned formation while maintaining the theoretically calculated tooth pitches.

What I claim is:

1. A method for rolling crowned gear teeth upon a workpiece having a workpiece axis wherein the workpiece is engaged by gear teeth forming roll means defining a rolling axis comprising rotating the workpiece about its workpiece axis while engaged by the roll means and simultaneously producing oscillation between the workpiece axis relative to the roll means and rolling axis by changing the angular relationship between said axes about a point of intersection of said axes, the rotational rate of rotation of the workpiece about its workpiece axis being different than the relative rate of oscillation of said axes.

2. A method in accordance with claim 1, wherein for said relative oscillation the workpiece axis of rotation is circulated on the shell ofa fictitious double cone with the cone axis being coincident with said rolling axis and the cone apex being disposed in the center of the workpiece axis of rotation whereby both a radial and axial crown is given to the formed teeth.

3. A method in accordance with claim 2, wherein the bases of said double cone are surfaces with continuous boundary line.

4. A method in accordance with claim 3, wherein said double cone bases are circular areas.

5. A method in accordance with claim 1, wherein for said relative oscillation the workpiece axis is oscillating in a triangular area with the triangular point being disposed in the center of the workpiece axis of rotation, said triangular area being coplanar with the plane through which extend the roll means axis of rotation and said rolling axis whereby a radial crown tooth is formed.

6. A method in accordance with claim 1, wherein for said relative oscillation the workpiece axis is oscillating in a triangular area with the triangular point being disposed in the center of the workpiece axis of rotation, said triangular area being arranged at right angle to the plane through which extend the roll means axis of rotation and said rolling axis whereby an axial crowning is formed on the toothing.

7. A method in accordance with claim 1, wherein the workpiece is moved axially relative to said rolling axis.

8. A method in accordance with claim 1, wherein the workpiece is first provided with an uncrowned tooth and said rolling axis is angularly inclined with respect to said workpiece axis in at least one direction with an amplitude corresponding to the desired crown to be formed.

9. A method in accordance with claim 1, wherein when rolling a bevel gear said point of intersection of the workpiece and rolling axis occurs at the intersection point of the axis of said roll means and the free side of a angle applied in the tooth center to the straight connecting line between said tooth center and the apex ofthe bevel gear cone.

10. A method in accordance with claim 9, wherein during the oscillation the workpiece axis is rotated about the axis of said roll means on a secondary cone arranged in a primary cone with the connecting line between said tooth center and the oscillation center as the primary cone generatrix, and an annular section of a spherical surface is covered along the pitch circle of the bevel gear and the roll cone base edge, respectively, the center of said sphere coinciding with the intersection point of the roll means axis and the workpiece axis.

11. A method in accordance with claim 10, wherein the generating angle and the volume of the secondary cone are dependent on the oscillation amplitude and consequently on the crown of the bevel gear teeth.

12. A method in accordance with claim 9, wherein during the oscillation the roll means axis is rotated on the shell of the secondary cone.

13. A method in accordance with claim 1, wherein the profiles of the crowned gear teeth are calculated and the teeth of the roll means is formed with counter profiles to said calculated profiles, the crown produced being obtained by roll means with the corresponding counter profiles.

14. A method in accordance with claim 1, wherein the workpiece gear tooth is crowned in an axial direction independently of the crown produced in a radial direction.

15. A method in accordance with claim 1, wherein the workpiece teeth are provided separately with axial and radial crowns, one crown being imparted by counter profiles on said roll means formed according to calculated tooth profiles for the workpiece and the other crown being imparted by said relative oscillation movement.

16. A method in accordance with claim 1, wherein the workpiece is preshaped by a cutting tool.

17. A machine tool for rolling crowned gear teeth comprising supporting means for rotatably supporting a gear blank to be rolled, said gear blank having an axis, roll means arranged at the periphery of the gear blank for rolling engagement therewith and defining a rolling axis, means adapted to generate a relative oscillating movement between said supporting means and said roll means by changing the relative angular position of the axis of said blank with respect to said rolling axis, and rotary drive means adapted to rotate said supporting means, said roll means and produce the oscillation movement generating means thereby imparting a rotational speed to the blank about its axis different from the frequency of said oscillating movement.

18. A machine tool in accordance with claim 17, wherein said oscillating movement generating means are punch tapers adapted to clamp the blank and arranged eccentrically with respect to the rolling axis of said roll means on the shell of a fictitious double cone the apex of which being situated in said rolling axis.

19. A machine tool in accordance with claim 17, wherein said oscillating movement generating means comprises a selfaligning thrust bearing arranged around said rolling axis for supporting one side of the blank and an axial projection on a pusher of said supporting means, said projection together with the blank supported thereon being capable ofhaving imparted thereto said oscillating movement.

20. A machine tool in accordance with claim 19, wherein said self-aligning thrust bearing is mounted in a master gear meshing with roll gears of said roll means and adapted to be driven by said drive means.

21. A machine tool in accordance with claim 20, wherein an application gearing is provided which is adapted to be driven in correspondence with the speed of the blank and to be adjusted radially by means of a gear thereof whereby the blank teeth may be exactly synchronized with the tooth gaps of said master gear and said roll gears, respectively.

22. A machine tool in accordance with claim 17, wherein said roll means comprising a plurality of roll gears is supported swingably about the rolling plane and the intersection point of the oscillation axis and the rolling axis, respectively, the swing of said roll means being adjustably limited by stop screws and being determinable by a measuring instrument.

23. A machine tool in accordance with claim 17, wherein the supporting means for a bevel gear to be rolled is supported on a journal by means ofa radial and an axial bearing and said oscillation movement generating means is provided by eccentric arrangement of said supporting means with respect to the axis of said roll means in a way that the intersection point of the rolling axis and the blank axis coincides with the intersection point ofthe rolling axis and the free side ofa angle applied in the tooth center to the straight connecting line between said tooth center and the apex of said bevel gear, and said roll means comprises at least one roll gear arranged at an angle of 90 with respect to said rolling axis.

24. A machine tool in accordance with claim 17, wherein said roll means is a roll gear supported on a tool support eccentrically rotatable by means ofa radial and an axial bearing.

25. A machine tool in accordance with claim 17, wherein said roll means comprises roll gears the teeth of which are calculated and shaped as counterprofile adapted to provide in the rolling operation an unidirectional crown on the blank gear teeth.

26. A machine tool in accordance with claim 25, wherein said roll gear counter profile is shaped for an axial crown on said blank teeth and the radial crown is obtained by said oscillating movement generating means.

27. A machine tool in accordance with claim 25, wherein said roll gear counterprofile is shaped for a radial crown on said blank gear teeth and the axial crown is obtained by said oscillating movement generating means.

[JNI'IED S'IA'IES PATENT OFFICE CERTIFICATE OF C 0 R R ECT l O N Patent No. 3 5 4 4 Dated June 15 1971 Inventofls) Frank F. Erdelyi It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the title page add:

Priority January 31, 1968 Germany P 16 52 654. 8

Si ned and sealed this 26th day of October 1971.

(SEAL) Attesc:

EDWARD M.; I".=:JTCl-IT:IR, ROBERT GOTTSGHALK Attestimg Officer Acting: Commissionerof Patents 

1. A method for rolling crowned gear teeth upon a workpiece having a workpiece axis wherein the workpiece is engaged by gear teeth forming roll means defining a rolling axis comprising rotating the workpiece about its workpiece axis while engaged by the roll means and simultaneously producing oscillation between the workpiece axis relative to the roll means and rolling axis by changing the angular relationship between said axes about a point of intersection of said axes, the rotational rate of rotation of the workpiece about its workpiece axis being different than the relative rate of oscillation of said axes.
 2. A method in accordance with claim 1, wherein for said relative oscillation the workpiece axis of rotation is circulated on the shell of a fictitious double cone with the cone axis being coincident with said rolling axis and the cone apex being disposed in the center of the workpiece axis of rotation whereby both a radial and axial crown is given to the formed teeth.
 3. A method in accordance with claim 2, wherein the bases of said double cone are surfaces with continuous boundary line.
 4. A method in accordance with claim 3, wherein said double cone bases are circular areas.
 5. A method in accordance with claim 1, wherein for said relative oscillation the workpiece axis is oscillating in a triangular area with the triangular point being disposed in the center of the workpiece axis of rotation, said triangular area being coplanar with the plane through which extend the roll means axis of rotation and said rolling axis whereby a radial crown tooth is formed.
 6. A method in accordance with claim 1, wherein for said relative oscillation the workpiece axis is oscillating in a triangular area with the triangular point being disposed in the center of the workpiece axis of rotation, said triangular area being arranged at right angle to the plane through which extend the roll means axis of rotation and said rolling axis whereby an axial crowning is formed on the toothing.
 7. A method in accordance with claim 1, wherein the workpiece is moved axially relative to said rolling axis.
 8. A method in accordance with claim 1, wherein the workpiece is first provided with an uncrowned tooth and said rolling axis is angularly inclined with respect to said workpiece axis in at least one direction with an amplitude corresponding to the desired crown to be formed.
 9. A method in accordance with claim 1, wherein when rolling a bevel gear said point of intersection of the workpiece and rolling axis occurs at the intersection point of the axis of said roll means and the free side of a 90* angle applied in the tooth center to the straight connecting line between said tooth center and the apex of the bevel gear cone.
 10. A method in accordance with claim 9, wherein during the oscillation the workpiece axis is rotated about the axis of said roll means on a secondary cone arranged in a primary cone with the connecting line between said tooth center and the oscillation center as the primary cone generatrix, and an annular section of a spherical surface is covered along the pitch circle of the bevel gear and the roll cone base edge, respectively, the center of said sphere coinciding with the intersection point of the roll means axis and the workpiece axis.
 11. A method in accordance with claim 10, wherein the generating angle and the volume of the secondary cone are dependent on the oscillation amplitude and consequently on the crown of the bevel gear teeth.
 12. A method in accordance with claim 9, wherein during the oscillation the roll means axis is rotated on the shell of the secondary cone.
 13. A method in accordance with claim 1, wherein the profiles of the crowned gear teeth are calculated and the teeth of the roll means is formed with counter profiles to said calculated profiles, the crown produced being obtained by roll means with the corresponding counter profiles.
 14. A method in accordance with claim 1, wherein the workpiece gear tooth is crowned in an axial direction independently of the crown produced in a radial direction.
 15. A method in accordance with claim 1, wherein the workpiece teeth are provided separately with axial and radial crowns, one crown being imparted by counter profiles on said roll means formed according to calculated tooth profiles for the workpiece and the other crown being imparted by said relative oscillation movement.
 16. A method in accordance with claim 1, wherein the workpiece is preshaped by a cutting tool.
 17. A machine tool for rolling crowned gear teeth comprising supporting means for rotatably supporting a gear blank to be rolled, said gear blank having an axis, roll means arranged at the periphery of the gear blank for rolling engagement therewith and defining a rolling axis, means adapted to generate a relative oscillating movement between said supporting means and said roll means by changing the relative angular position of the axis of said blank with respect to said rolling axis, and rotary drive means adapted to rotate said supporting means, said roll means and produce the oscillation movement generating means thereby imparting a rotational speed to the blank about its axis different from the frequency of said oscillating movement.
 18. A machine tool in accordance with claim 17, wherein said oscillating movement generating means are punch tapers adapted to clamp the blank and arranged eccentrically with respect to the rolling axis of said roll means on the shell of a fictitious double cone the apex of which being situated in said rolling axis.
 19. A machine tool in accordance with claim 17, wherein said oscillating movement generating means comprises a self-aligning thrust bearing arranged around said rolling axis for supporting one side of the blank and an axial projection on a pusher of said supporting means, said projection together with the blank supported thereon being capable of having imparted thereto said oscillating movement.
 20. A machine tool in accordance with claim 19, wherein said self-aligning thrust bearing is mounted in a master gear meshing with roll gears of said roll means and adapted to be driven by said drive means.
 21. A machine tool in accordance with claim 20, wherein an application gearing is provided which is adapted to be driven in correspondence with the speed of the blank and to be adjusted radially by means of a gear thereof whereby the blank teeth may be exactly synchronized with the tooth gaps of said master gear and said roll gears, respectively.
 22. A machine tool in accordance with claim 17, wherein said roll means comprising a plurality of roll gears is supported swingably about the rolling plane and the intersection point of the oscillation axis and the rolling axis, respectively, the swing of said roll means being adjustably limited by stop screws and being determinable by a measuring instrument.
 23. A machine tool in accordance with claim 17, wherein the supporting means for a bevel gear to be rolled is supported on a journal by means of a radial and an axial bearing and said oscillation movement generating means is provided by eccentric arrangement of said supporting means with respect to the axis of said roll means in a way that the intersection point of the rolling axis and the blank axis coincides with the intersection point of the rolling axis and the free side of a 90* angle applied in the tooth center to the straight connecting line between said tooth center and the apex of said bevel gear, and said roll means comprises at least one roll gear arranged at an angle of 90* with respect to said rolling axis.
 24. A machine tool in accordance with claim 17, wherein said roll means is a roll gear supported on a tool support eccentrically rotatable by means of a radial and an axial bearing.
 25. A machine tool in accordance with claim 17, wherein said roll means comprises roll gears the teeth of which are calculated and shaped as counterprofile adapted to provide in the rolling operation an unidirectional crown on the blank gear teeth.
 26. A machine tool in accordance with claim 25, wherein said roll gear counter profile is shaped for an axial crown on said blank teeth and the radial crown is obtained by said oscillating movement generating means.
 27. A machine tool in accordance with claim 25, wherein said roll gear counterprofile is shaped for a radial crown on said blank gear teeth and the axial crown is obtained by said oscillating movement generating means. 